Non-rigid airships in general use a lifting gas, such as helium, and air to allow for the ascent and descent of the airship while maintaining a higher gas pressure on the inside of the airship than on the outside of the airship. Because the interaction or mixing of the lifting gas and air is unwanted, techniques aimed at separating the lifting gas from the air have been developed and have been successful with respect to conventional airships that do not attain high altitude (high altitude generally being considered 40,000 ft. and above). However, utilizing such conventional methods in a high altitude airship suffers from several drawbacks.
A conventional, non-rigid airship 10 that does not ascend to high altitudes, as shown in FIGS. 1A and 1B, typically comprises a hull or envelope 12 within which a number of ballonets 14,16 are disposed. The ballonets 14,16 are holding balloons that are made from a flexible, impermeable material that are attached to the interior of the envelope 12 of the airship 10, and are utilized to store and separate air from the helium held within the remaining portion of the envelope 12. As the airship 10 ascends to altitude, the air stored in each ballonet 14,16 is exhausted through a number of valve/blowers 18,20, causing the ballonets 14,16 to deflate, as shown in FIG. 1A. The helium within the envelope 12 expands while the airship 10 ascends to the desired altitude. It will be appreciated that expansion of the helium also forces air out of the ballonets. Resultantly, during the deflation of the ballonets 14,16, the material comprising the ballonets 14,16 tends to collapse and bunch so as to take on an unsymmetrical orientation with respect to the envelope 12.
In order to maintain pressure during descent, air is forced back into each ballonet 14,16 using the valve/blowers 18,20 causing the ballonets 14,16 to inflate, as shown in FIG. 1B. Thus, it should be clear that the material comprising the ballonets 14,16 traverses, or moves from a deflated condition to an inflated condition as air is blown into the ballonets 14,16. Likewise, the material comprising the ballonets moves from an inflated to a deflated condition as air is pushed out of the ballonets 14,16.
High altitude airships are structures that resemble conventional airships, but may be significantly larger. For example, the hull or envelope of a high altitude airship may comprise a volume of several million cubic feet. Due to the large variation in pressure and temperature that occurs as the high altitude airship moves from ground to high altitude and vice versa, it is required that the helium within the high altitude airship expand to a greater degree than that required by conventional airships. Additionally, a high altitude airship requires that a larger amount of air be expelled from its envelope than that of conventional airships. As such, to ascend the high altitude airship to a high altitude, large ballonets would be required to accommodate the large quantity of lifting gas expansion that would occur within the envelope of the high altitude airship. Utilizing large ballonets, however, is impractical for high altitude airships because the added weight would act to impede the attainment of high altitudes. Furthermore, because of the increased amount of material needed for the ballonets of a high altitude airship, significant bunching and twisting of the ballonet material would result when the ballonets are deflated, thus leading to an imbalanced condition within the envelope. The balance of the high altitude airship would be further hampered as the lifting gas would be free to accumulate in any region within the hull or envelope of the airship making it difficult to maintain control of the airship. For example, if the lifting gas accumulates toward the aft portion of the airship, this would cause the airship to become nose heavy, making it difficult to fly or to ascend.
Therefore, there is a need for a lifting gas cell system that can accommodate the large expansion and contraction of the lifting gas that will occur inside a high altitude airship. Additionally, there is a need for a lifting gas cell system for a high altitude airship that is lightweight. Still yet, there is a need for a lifting gas cell system that provides a plurality of cells to distribute the lifting gas evenly along the length of the hull of the airship, to maintain the balance, stability, and control of the airship.